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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.43 by dl, Mon Aug 24 23:08:18 2009 UTC vs.
Revision 1.69 by jsr166, Sat Dec 4 22:00:05 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	<	import java.util.concurrent.*;
10	<
9	>	import java.util.concurrent.TimeUnit;
10	>	import java.util.concurrent.TimeoutException;
11		import java.util.concurrent.atomic.AtomicReference;
12		import java.util.concurrent.locks.LockSupport;
13
#	Line 34 | Line 34 | import java.util.concurrent.locks.LockSu
34		* Phaser} may be repeatedly awaited.  Method {@link
35		* #arriveAndAwaitAdvance} has effect analogous to {@link
36		* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
37	<	* generation of a {@code Phaser} has an associated phase number. The
38	<	* phase number starts at zero, and advances when all parties arrive
39	<	* at the barrier, wrapping around to zero after reaching {@code
37	>	* generation of a phaser has an associated phase number. The phase
38	>	* number starts at zero, and advances when all parties arrive at the
39	>	* phaser, wrapping around to zero after reaching {@code
40		* Integer.MAX_VALUE}. The use of phase numbers enables independent
41	<	* control of actions upon arrival at a barrier and upon awaiting
41	>	* control of actions upon arrival at a phaser and upon awaiting
42		* others, via two kinds of methods that may be invoked by any
43		* registered party:
44		*
45		* <ul>
46		*
47		*   <li> <b>Arrival.</b> Methods {@link #arrive} and
48	<	*       {@link #arriveAndDeregister} record arrival at a
49	<	*       barrier. These methods do not block, but return an associated
50	<	*       <em>arrival phase number</em>; that is, the phase number of
51	<	*       the barrier to which the arrival applied. When the final
52	<	*       party for a given phase arrives, an optional barrier action
53	<	*       is performed and the phase advances.  Barrier actions,
54	<	*       performed by the party triggering a phase advance, are
55	<	*       arranged by overriding method {@link #onAdvance(int, int)},
56	<	*       which also controls termination. Overriding this method is
57	<	*       similar to, but more flexible than, providing a barrier
58	<	*       action to a {@code CyclicBarrier}.
48	>	*       {@link #arriveAndDeregister} record arrival.  These methods
49	>	*       do not block, but return an associated <em>arrival phase
50	>	*       number</em>; that is, the phase number of the phaser to which
51	>	*       the arrival applied. When the final party for a given phase
52	>	*       arrives, an optional action is performed and the phase
53	>	*       advances.  These actions are performed by the party
54	>	*       triggering a phase advance, and are arranged by overriding
55	>	*       method {@link #onAdvance(int, int)}, which also controls
56	>	*       termination. Overriding this method is similar to, but more
57	>	*       flexible than, providing a barrier action to a {@code
58	>	*       CyclicBarrier}.
59		*
60		*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61		*       argument indicating an arrival phase number, and returns when
62	<	*       the barrier advances to (or is already at) a different phase.
62	>	*       the phaser advances to (or is already at) a different phase.
63		*       Unlike similar constructions using {@code CyclicBarrier},
64		*       method {@code awaitAdvance} continues to wait even if the
65		*       waiting thread is interrupted. Interruptible and timeout
66		*       versions are also available, but exceptions encountered while
67		*       tasks wait interruptibly or with timeout do not change the
68	<	*       state of the barrier. If necessary, you can perform any
68	>	*       state of the phaser. If necessary, you can perform any
69		*       associated recovery within handlers of those exceptions,
70		*       often after invoking {@code forceTermination}.  Phasers may
71		*       also be used by tasks executing in a {@link ForkJoinPool},
#	Line 74 | Line 74 | import java.util.concurrent.locks.LockSu
74		*
75		* </ul>
76		*
77	<	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	<	* <em>termination</em> state in which all synchronization methods
79	<	* immediately return without updating phaser state or waiting for
80	<	* advance, and indicating (via a negative phase value) that execution
81	<	* is complete.  Termination is triggered when an invocation of {@code
82	<	* onAdvance} returns {@code true}.  As illustrated below, when
83	<	* phasers control actions with a fixed number of iterations, it is
84	<	* often convenient to override this method to cause termination when
85	<	* the current phase number reaches a threshold. Method {@link
86	<	* #forceTermination} is also available to abruptly release waiting
87	<	* threads and allow them to terminate.
88	<	*
89	<	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
90	<	* in tree structures) to reduce contention. Phasers with large
91	<	* numbers of parties that would otherwise experience heavy
77	>	* <p> <b>Termination.</b> A phaser may enter a <em>termination</em>
78	>	* state, that may be checked using method {@link #isTerminated}. Upon
79	>	* termination, all synchronization methods immediately return without
80	>	* waiting for advance, as indicated by a negative return value.
81	>	* Similarly, attempts to register upon termination have no effect.
82	>	* Termination is triggered when an invocation of {@code onAdvance}
83	>	* returns {@code true}. The default implementation returns {@code
84	>	* true} if a deregistration has caused the number of registered
85	>	* parties to become zero.  As illustrated below, when phasers control
86	>	* actions with a fixed number of iterations, it is often convenient
87	>	* to override this method to cause termination when the current phase
88	>	* number reaches a threshold. Method {@link #forceTermination} is
89	>	* also available to abruptly release waiting threads and allow them
90	>	* to terminate.
91	>	*
92	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
93	>	* constructed in tree structures) to reduce contention. Phasers with
94	>	* large numbers of parties that would otherwise experience heavy
95		* synchronization contention costs may instead be set up so that
96		* groups of sub-phasers share a common parent.  This may greatly
97		* increase throughput even though it incurs greater per-operation
98		* overhead.
99		*
100	+	* <p>In a tree of tiered phasers, registration and deregistration of
101	+	* child phasers with their parent are managed automatically.
102	+	* Whenever the number of registered parties of a child phaser becomes
103	+	* non-zero (as established in the {@link #Phaser(Phaser,int)}
104	+	* constructor, {@link #register}, or {@link #bulkRegister}), the
105	+	* child phaser is registered with its parent.  Whenever the number of
106	+	* registered parties becomes zero as the result of an invocation of
107	+	* {@link #arriveAndDeregister}, the child phaser is deregistered
108	+	* from its parent.
109	+	*
110		* <p><b>Monitoring.</b> While synchronization methods may be invoked
111		* only by registered parties, the current state of a phaser may be
112		* monitored by any caller.  At any given moment there are {@link
#	Line 109 | Line 122 | import java.util.concurrent.locks.LockSu
122		* <p><b>Sample usages:</b>
123		*
124		* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
125	<	* to control a one-shot action serving a variable number of
126	<	* parties. The typical idiom is for the method setting this up to
127	<	* first register, then start the actions, then deregister, as in:
125	>	* to control a one-shot action serving a variable number of parties.
126	>	* The typical idiom is for the method setting this up to first
127	>	* register, then start the actions, then deregister, as in:
128		*
129		*  <pre> {@code
130		* void runTasks(List<Runnable> tasks) {
#	Line 142 | Line 155 | import java.util.concurrent.locks.LockSu
155		*     }
156		*   };
157		*   phaser.register();
158	<	*   for (Runnable task : tasks) {
158	>	*   for (final Runnable task : tasks) {
159		*     phaser.register();
160		*     new Thread() {
161		*       public void run() {
162		*         do {
163		*           task.run();
164		*           phaser.arriveAndAwaitAdvance();
165	<	*         } while(!phaser.isTerminated();
165	>	*         } while (!phaser.isTerminated());
166		*       }
167		*     }.start();
168		*   }
#	Line 158 | Line 171 | import java.util.concurrent.locks.LockSu
171		*
172		* If the main task must later await termination, it
173		* may re-register and then execute a similar loop:
174	<	* <pre> {@code
174	>	*  <pre> {@code
175		*   // ...
176		*   phaser.register();
177		*   while (!phaser.isTerminated())
178	<	*     phaser.arriveAndAwaitAdvance();
166	<	* }</pre>
178	>	*     phaser.arriveAndAwaitAdvance();}</pre>
179		*
180	<	* Related constructions may be used to await particular phase numbers
180	>	* <p>Related constructions may be used to await particular phase numbers
181		* in contexts where you are sure that the phase will never wrap around
182		* {@code Integer.MAX_VALUE}. For example:
183		*
184	<	* <pre> {@code
185	<	*   void awaitPhase(Phaser phaser, int phase) {
186	<	*     int p = phaser.register(); // assumes caller not already registered
187	<	*     while (p < phase) {
188	<	*       if (phaser.isTerminated())
189	<	*         // ... deal with unexpected termination
190	<	*       else
191	<	*         p = phaser.arriveAndAwaitAdvance();
180	<	*     }
181	<	*     phaser.arriveAndDeregister();
184	>	*  <pre> {@code
185	>	* void awaitPhase(Phaser phaser, int phase) {
186	>	*   int p = phaser.register(); // assumes caller not already registered
187	>	*   while (p < phase) {
188	>	*     if (phaser.isTerminated())
189	>	*       // ... deal with unexpected termination
190	>	*     else
191	>	*       p = phaser.arriveAndAwaitAdvance();
192		*   }
193	<	* }</pre>
193	>	*   phaser.arriveAndDeregister();
194	>	* }}</pre>
195		*
196		*
197	<	* <p>To create a set of tasks using a tree of phasers,
198	<	* you could use code of the following form, assuming a
199	<	* Task class with a constructor accepting a phaser that
200	<	* it registers for upon construction:
197	>	* <p>To create a set of {@code n} tasks using a tree of phasers, you
198	>	* could use code of the following form, assuming a Task class with a
199	>	* constructor accepting a {@code Phaser} that it registers with upon
200	>	* construction. After invocation of {@code build(new Task[n], 0, n,
201	>	* new Phaser())}, these tasks could then be started, for example by
202	>	* submitting to a pool:
203	>	*
204		*  <pre> {@code
205	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
206	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
207	<	*   if (step > 1) {
208	<	*     int i = lo;
209	<	*     while (i < hi) {
196	<	*       int r = Math.min(i + step, hi);
197	<	*       build(actions, i, r, new Phaser(b));
198	<	*       i = r;
205	>	* void build(Task[] tasks, int lo, int hi, Phaser ph) {
206	>	*   if (hi - lo > TASKS_PER_PHASER) {
207	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
208	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
209	>	*       build(tasks, i, j, new Phaser(ph));
210		*     }
211		*   } else {
212		*     for (int i = lo; i < hi; ++i)
213	<	*       actions[i] = new Task(b);
214	<	*       // assumes new Task(b) performs b.register()
213	>	*       tasks[i] = new Task(ph);
214	>	*       // assumes new Task(ph) performs ph.register()
215		*   }
216	<	* }
206	<	* // .. initially called, for n tasks via
207	<	* build(new Task[n], 0, n, new Phaser());}</pre>
216	>	* }}</pre>
217		*
218		* The best value of {@code TASKS_PER_PHASER} depends mainly on
219	<	* expected barrier synchronization rates. A value as low as four may
220	<	* be appropriate for extremely small per-barrier task bodies (thus
219	>	* expected synchronization rates. A value as low as four may
220	>	* be appropriate for extremely small per-phase task bodies (thus
221		* high rates), or up to hundreds for extremely large ones.
222		*
214	–	* </pre>
215	–	*
223		* <p><b>Implementation notes</b>: This implementation restricts the
224		* maximum number of parties to 65535. Attempts to register additional
225		* parties result in {@code IllegalStateException}. However, you can and
#	Line 230 | Line 237 | public class Phaser {
237		*/
238
239		/**
240	<	* Barrier state representation. Conceptually, a barrier contains
234	<	* four values:
235	<	*
236	<	* * parties -- the number of parties to wait (16 bits)
237	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
238	<	* * phase -- the generation of the barrier (31 bits)
239	<	* * terminated -- set if barrier is terminated (1 bit)
240	<	*
241	<	* However, to efficiently maintain atomicity, these values are
242	<	* packed into a single (atomic) long. Termination uses the sign
243	<	* bit of 32 bit representation of phase, so phase is set to -1 on
244	<	* termination. Good performance relies on keeping state decoding
245	<	* and encoding simple, and keeping race windows short.
240	>	* Primary state representation, holding four fields:
241		*
242	<	* Note: there are some cheats in arrive() that rely on unarrived
243	<	* count being lowest 16 bits.
242	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
243	>	* * parties -- the number of parties to wait              (bits 16-31)
244	>	* * phase -- the generation of the barrier                (bits 32-62)
245	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
246	>	*
247	>	* Except that a phaser with no registered parties is
248	>	* distinguished with the otherwise illegal state of having zero
249	>	* parties and one unarrived parties (encoded as EMPTY below).
250	>	*
251	>	* To efficiently maintain atomicity, these values are packed into
252	>	* a single (atomic) long. Good performance relies on keeping
253	>	* state decoding and encoding simple, and keeping race windows
254	>	* short.
255	>	*
256	>	* All state updates are performed via CAS except initial
257	>	* registration of a sub-phaser (i.e., one with a non-null
258	>	* parent).  In this (relatively rare) case, we use built-in
259	>	* synchronization to lock while first registering with its
260	>	* parent.
261	>	*
262	>	* The phase of a subphaser is allowed to lag that of its
263	>	* ancestors until it is actually accessed.  Method reconcileState
264	>	* is usually attempted only only when the number of unarrived
265	>	* parties appears to be zero, which indicates a potential lag in
266	>	* updating phase after the root advanced.
267		*/
268		private volatile long state;
269
270	<	private static final int ushortMask = 0xffff;
271	<	private static final int phaseMask  = 0x7fffffff;
270	>	private static final int  MAX_PARTIES     = 0xffff;
271	>	private static final int  MAX_PHASE       = 0x7fffffff;
272	>	private static final int  PARTIES_SHIFT   = 16;
273	>	private static final int  PHASE_SHIFT     = 32;
274	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
275	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
276	>	private static final long TERMINATION_BIT = 1L << 63;
277	>
278	>	// some special values
279	>	private static final int  ONE_ARRIVAL     = 1;
280	>	private static final int  ONE_PARTY       = 1 << PARTIES_SHIFT;
281	>	private static final int  EMPTY           = 1;
282	>
283	>	// The following unpacking methods are usually manually inlined
284
285		private static int unarrivedOf(long s) {
286	<	return (int) (s & ushortMask);
286	>	int counts = (int)s;
287	>	return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK;
288		}
289
290		private static int partiesOf(long s) {
291	<	return ((int) s) >>> 16;
291	>	return (int)s >>> PARTIES_SHIFT;
292		}
293
294		private static int phaseOf(long s) {
295	<	return (int) (s >>> 32);
295	>	return (int) (s >>> PHASE_SHIFT);
296		}
297
298		private static int arrivedOf(long s) {
299	<	return partiesOf(s) - unarrivedOf(s);
300	<	}
301	<
271	<	private static long stateFor(int phase, int parties, int unarrived) {
272	<	return ((((long) phase) << 32) | (((long) parties) << 16) |
273	<	(long) unarrived);
274	<	}
275	<
276	<	private static long trippedStateFor(int phase, int parties) {
277	<	long lp = (long) parties;
278	<	return (((long) phase) << 32) | (lp << 16) | lp;
279	<	}
280	<
281	<	/**
282	<	* Returns message string for bad bounds exceptions.
283	<	*/
284	<	private static String badBounds(int parties, int unarrived) {
285	<	return ("Attempt to set " + unarrived +
286	<	" unarrived of " + parties + " parties");
299	>	int counts = (int)s;
300	>	return (counts == EMPTY) ? 0 :
301	>	(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK);
302		}
303
304		/**
#	Line 292 | Line 307 | public class Phaser {
307		private final Phaser parent;
308
309		/**
310	<	* The root of phaser tree. Equals this if not in a tree.  Used to
296	<	* support faster state push-down.
310	>	* The root of phaser tree. Equals this if not in a tree.
311		*/
312		private final Phaser root;
313
300	–	// Wait queues
301	–
314		/**
315		* Heads of Treiber stacks for waiting threads. To eliminate
316	<	* contention while releasing some threads while adding others, we
316	>	* contention when releasing some threads while adding others, we
317		* use two of them, alternating across even and odd phases.
318	+	* Subphasers share queues with root to speed up releases.
319		*/
320	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
321	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
320	>	private final AtomicReference<QNode> evenQ;
321	>	private final AtomicReference<QNode> oddQ;
322
323		private AtomicReference<QNode> queueFor(int phase) {
324		return ((phase & 1) == 0) ? evenQ : oddQ;
325		}
326
327		/**
328	<	* Returns current state, first resolving lagged propagation from
329	<	* root if necessary.
328	>	* Returns message string for bounds exceptions on arrival.
329	>	*/
330	>	private String badArrive(long s) {
331	>	return "Attempted arrival of unregistered party for " +
332	>	stateToString(s);
333	>	}
334	>
335	>	/**
336	>	* Returns message string for bounds exceptions on registration.
337	>	*/
338	>	private String badRegister(long s) {
339	>	return "Attempt to register more than " +
340	>	MAX_PARTIES + " parties for " + stateToString(s);
341	>	}
342	>
343	>	/**
344	>	* Main implementation for methods arrive and arriveAndDeregister.
345	>	* Manually tuned to speed up and minimize race windows for the
346	>	* common case of just decrementing unarrived field.
347	>	*
348	>	* @param deregister false for arrive, true for arriveAndDeregister
349		*/
350	<	private long getReconciledState() {
351	<	return (parent == null) ? state : reconcileState();
350	>	private int doArrive(boolean deregister) {
351	>	int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL;
352	>	final Phaser root = this.root;
353	>	for (;;) {
354	>	long s = (root == this) ? state : reconcileState();
355	>	int phase = (int)(s >>> PHASE_SHIFT);
356	>	int counts = (int)s;
357	>	int unarrived = (counts & UNARRIVED_MASK) - 1;
358	>	if (phase < 0)
359	>	return phase;
360	>	else if (counts == EMPTY || unarrived < 0) {
361	>	if (root == this || reconcileState() == s)
362	>	throw new IllegalStateException(badArrive(s));
363	>	}
364	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
365	>	if (unarrived == 0) {
366	>	long n = s & PARTIES_MASK;  // base of next state
367	>	int nextUnarrived = ((int)n) >>> PARTIES_SHIFT;
368	>	if (root != this)
369	>	return parent.doArrive(nextUnarrived == 0);
370	>	if (onAdvance(phase, nextUnarrived))
371	>	n |= TERMINATION_BIT;
372	>	else if (nextUnarrived == 0)
373	>	n |= EMPTY;
374	>	else
375	>	n |= nextUnarrived;
376	>	n |= ((long)((phase + 1) & MAX_PHASE)) << PHASE_SHIFT;
377	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
378	>	releaseWaiters(phase);
379	>	}
380	>	return phase;
381	>	}
382	>	}
383		}
384
385		/**
386	<	* Recursively resolves state.
386	>	* Implementation of register, bulkRegister
387	>	*
388	>	* @param registrations number to add to both parties and
389	>	* unarrived fields. Must be greater than zero.
390	>	*/
391	>	private int doRegister(int registrations) {
392	>	// adjustment to state
393	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
394	>	Phaser par = parent;
395	>	int phase;
396	>	for (;;) {
397	>	long s = state;
398	>	int counts = (int)s;
399	>	int parties = counts >>> PARTIES_SHIFT;
400	>	int unarrived = counts & UNARRIVED_MASK;
401	>	if (registrations > MAX_PARTIES - parties)
402	>	throw new IllegalStateException(badRegister(s));
403	>	else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
404	>	break;
405	>	else if (counts != EMPTY) {             // not 1st registration
406	>	if (par == null || reconcileState() == s) {
407	>	if (unarrived == 0)             // wait out advance
408	>	root.internalAwaitAdvance(phase, null);
409	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset,
410	>	s, s + adj))
411	>	break;
412	>	}
413	>	}
414	>	else if (par == null) {                 // 1st root registration
415	>	long next = (((long) phase) << PHASE_SHIFT) | adj;
416	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
417	>	break;
418	>	}
419	>	else {
420	>	synchronized (this) {               // 1st sub registration
421	>	if (state == s) {               // recheck under lock
422	>	par.doRegister(1);
423	>	do {                        // force current phase
424	>	phase = (int)(root.state >>> PHASE_SHIFT);
425	>	// assert phase < 0 || (int)state == EMPTY;
426	>	} while (!UNSAFE.compareAndSwapLong
427	>	(this, stateOffset, state,
428	>	(((long) phase) << PHASE_SHIFT) | adj));
429	>	break;
430	>	}
431	>	}
432	>	}
433	>	}
434	>	return phase;
435	>	}
436	>
437	>	/**
438	>	* Resolves lagged phase propagation from root if necessary.
439		*/
440		private long reconcileState() {
441	<	Phaser p = parent;
441	>	Phaser rt = root;
442		long s = state;
443	<	if (p != null) {
444	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
445	<	long parentState = p.getReconciledState();
446	<	int parentPhase = phaseOf(parentState);
447	<	int phase = phaseOf(s = state);
448	<	if (phase != parentPhase) {
449	<	long next = trippedStateFor(parentPhase, partiesOf(s));
450	<	if (casState(s, next)) {
451	<	releaseWaiters(phase);
452	<	s = next;
453	<	}
443	>	if (rt != this) {
444	>	int phase;
445	>	while ((phase = (int)(rt.state >>> PHASE_SHIFT)) !=
446	>	(int)(s >>> PHASE_SHIFT)) {
447	>	// assert phase < 0 || unarrivedOf(s) == 0
448	>	long t;                             // to reread s
449	>	long p = s & PARTIES_MASK;          // unshifted parties field
450	>	long n = (((long) phase) << PHASE_SHIFT) | p;
451	>	if (phase >= 0) {
452	>	if (p == 0L)
453	>	n |= EMPTY;                 // reset to empty
454	>	else
455	>	n |= p >>> PARTIES_SHIFT;   // set unarr to parties
456		}
457	+	if ((t = state) == s &&
458	+	UNSAFE.compareAndSwapLong(this, stateOffset, s, s = n))
459	+	break;
460	+	s = t;
461		}
462		}
463		return s;
464		}
465
466		/**
467	<	* Creates a new phaser without any initially registered parties,
468	<	* initial phase number 0, and no parent. Any thread using this
467	>	* Creates a new phaser with no initially registered parties, no
468	>	* parent, and initial phase number 0. Any thread using this
469		* phaser will need to first register for it.
470		*/
471		public Phaser() {
472	<	this(null);
472	>	this(null, 0);
473		}
474
475		/**
476	<	* Creates a new phaser with the given numbers of registered
477	<	* unarrived parties, initial phase number 0, and no parent.
476	>	* Creates a new phaser with the given number of registered
477	>	* unarrived parties, no parent, and initial phase number 0.
478		*
479	<	* @param parties the number of parties required to trip barrier
479	>	* @param parties the number of parties required to advance to the
480	>	* next phase
481		* @throws IllegalArgumentException if parties less than zero
482		* or greater than the maximum number of parties supported
483		*/
#	Line 364 | Line 486 | public class Phaser {
486		}
487
488		/**
489	<	* Creates a new phaser with the given parent, without any
368	<	* initially registered parties. If parent is non-null this phaser
369	<	* is registered with the parent and its initial phase number is
370	<	* the same as that of parent phaser.
489	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
490		*
491		* @param parent the parent phaser
492		*/
493		public Phaser(Phaser parent) {
494	<	int phase = 0;
376	<	this.parent = parent;
377	<	if (parent != null) {
378	<	this.root = parent.root;
379	<	phase = parent.register();
380	<	}
381	<	else
382	<	this.root = this;
383	<	this.state = trippedStateFor(phase, 0);
494	>	this(parent, 0);
495		}
496
497		/**
498	<	* Creates a new phaser with the given parent and numbers of
499	<	* registered unarrived parties. If parent is non-null, this phaser
500	<	* is registered with the parent and its initial phase number is
501	<	* the same as that of parent phaser.
498	>	* Creates a new phaser with the given parent and number of
499	>	* registered unarrived parties.  When the given parent is non-null
500	>	* and the given number of parties is greater than zero, this
501	>	* child phaser is registered with its parent.
502		*
503		* @param parent the parent phaser
504	<	* @param parties the number of parties required to trip barrier
504	>	* @param parties the number of parties required to advance to the
505	>	* next phase
506		* @throws IllegalArgumentException if parties less than zero
507		* or greater than the maximum number of parties supported
508		*/
509		public Phaser(Phaser parent, int parties) {
510	<	if (parties < 0 || parties > ushortMask)
510	>	if (parties >>> PARTIES_SHIFT != 0)
511		throw new IllegalArgumentException("Illegal number of parties");
512		int phase = 0;
513		this.parent = parent;
514		if (parent != null) {
515	<	this.root = parent.root;
516	<	phase = parent.register();
515	>	final Phaser root = parent.root;
516	>	this.root = root;
517	>	this.evenQ = root.evenQ;
518	>	this.oddQ = root.oddQ;
519	>	if (parties != 0)
520	>	phase = parent.doRegister(1);
521		}
522	<	else
522	>	else {
523		this.root = this;
524	<	this.state = trippedStateFor(phase, parties);
524	>	this.evenQ = new AtomicReference<QNode>();
525	>	this.oddQ = new AtomicReference<QNode>();
526	>	}
527	>	this.state = (parties == 0) ? (long) EMPTY :
528	>	((((long) phase) << PHASE_SHIFT) |
529	>	(((long) parties) << PARTIES_SHIFT) |
530	>	((long) parties));
531		}
532
533		/**
534	<	* Adds a new unarrived party to this phaser.
535	<	*
536	<	* @return the arrival phase number to which this registration applied
534	>	* Adds a new unarrived party to this phaser.  If an ongoing
535	>	* invocation of {@link #onAdvance} is in progress, this method
536	>	* may await its completion before returning.  If this phaser has
537	>	* a parent, and this phaser previously had no registered parties,
538	>	* this child phaser is also registered with its parent. If
539	>	* this phaser is terminated, the attempt to register has
540	>	* no effect, and a negative value is returned.
541	>	*
542	>	* @return the arrival phase number to which this registration
543	>	* applied.  If this value is negative, then this phaser has
544	>	* terminated, in which case registration has no effect.
545		* @throws IllegalStateException if attempting to register more
546		* than the maximum supported number of parties
547		*/
#	Line 421 | Line 551 | public class Phaser {
551
552		/**
553		* Adds the given number of new unarrived parties to this phaser.
554	<	*
555	<	* @param parties the number of parties required to trip barrier
556	<	* @return the arrival phase number to which this registration applied
554	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
555	>	* this method may await its completion before returning.  If this
556	>	* phaser has a parent, and the given number of parties is greater
557	>	* than zero, and this phaser previously had no registered
558	>	* parties, this child phaser is also registered with its parent.
559	>	* If this phaser is terminated, the attempt to register has no
560	>	* effect, and a negative value is returned.
561	>	*
562	>	* @param parties the number of additional parties required to
563	>	* advance to the next phase
564	>	* @return the arrival phase number to which this registration
565	>	* applied.  If this value is negative, then this phaser has
566	>	* terminated, in which case registration has no effect.
567		* @throws IllegalStateException if attempting to register more
568		* than the maximum supported number of parties
569	+	* @throws IllegalArgumentException if {@code parties < 0}
570		*/
571		public int bulkRegister(int parties) {
572		if (parties < 0)
#	Line 436 | Line 577 | public class Phaser {
577		}
578
579		/**
580	<	* Shared code for register, bulkRegister
581	<	*/
582	<	private int doRegister(int registrations) {
583	<	int phase;
584	<	for (;;) {
585	<	long s = getReconciledState();
445	<	phase = phaseOf(s);
446	<	int unarrived = unarrivedOf(s) + registrations;
447	<	int parties = partiesOf(s) + registrations;
448	<	if (phase < 0)
449	<	break;
450	<	if (parties > ushortMask || unarrived > ushortMask)
451	<	throw new IllegalStateException(badBounds(parties, unarrived));
452	<	if (phase == phaseOf(root.state) &&
453	<	casState(s, stateFor(phase, parties, unarrived)))
454	<	break;
455	<	}
456	<	return phase;
457	<	}
458	<
459	<	/**
460	<	* Arrives at the barrier, but does not wait for others.  (You can
461	<	* in turn wait for others via {@link #awaitAdvance}).  It is an
462	<	* unenforced usage error for an unregistered party to invoke this
463	<	* method.
580	>	* Arrives at this phaser, without waiting for others to arrive.
581	>	*
582	>	* <p>It is a usage error for an unregistered party to invoke this
583	>	* method.  However, this error may result in an {@code
584	>	* IllegalStateException} only upon some subsequent operation on
585	>	* this phaser, if ever.
586		*
587		* @return the arrival phase number, or a negative value if terminated
588		* @throws IllegalStateException if not terminated and the number
589		* of unarrived parties would become negative
590		*/
591		public int arrive() {
592	<	int phase;
471	<	for (;;) {
472	<	long s = state;
473	<	phase = phaseOf(s);
474	<	if (phase < 0)
475	<	break;
476	<	int parties = partiesOf(s);
477	<	int unarrived = unarrivedOf(s) - 1;
478	<	if (unarrived > 0) {        // Not the last arrival
479	<	if (casState(s, s - 1)) // s-1 adds one arrival
480	<	break;
481	<	}
482	<	else if (unarrived == 0) {  // the last arrival
483	<	Phaser par = parent;
484	<	if (par == null) {      // directly trip
485	<	if (casState
486	<	(s,
487	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
488	<	((phase + 1) & phaseMask), parties))) {
489	<	releaseWaiters(phase);
490	<	break;
491	<	}
492	<	}
493	<	else {                  // cascade to parent
494	<	if (casState(s, s - 1)) { // zeroes unarrived
495	<	par.arrive();
496	<	reconcileState();
497	<	break;
498	<	}
499	<	}
500	<	}
501	<	else if (phase != phaseOf(root.state)) // or if unreconciled
502	<	reconcileState();
503	<	else
504	<	throw new IllegalStateException(badBounds(parties, unarrived));
505	<	}
506	<	return phase;
592	>	return doArrive(false);
593		}
594
595		/**
596	<	* Arrives at the barrier and deregisters from it without waiting
597	<	* for others. Deregistration reduces the number of parties
598	<	* required to trip the barrier in future phases.  If this phaser
596	>	* Arrives at this phaser and deregisters from it without waiting
597	>	* for others to arrive. Deregistration reduces the number of
598	>	* parties required to advance in future phases.  If this phaser
599		* has a parent, and deregistration causes this phaser to have
600	<	* zero parties, this phaser also arrives at and is deregistered
601	<	* from its parent.  It is an unenforced usage error for an
602	<	* unregistered party to invoke this method.
600	>	* zero parties, this phaser is also deregistered from its parent.
601	>	*
602	>	* <p>It is a usage error for an unregistered party to invoke this
603	>	* method.  However, this error may result in an {@code
604	>	* IllegalStateException} only upon some subsequent operation on
605	>	* this phaser, if ever.
606		*
607		* @return the arrival phase number, or a negative value if terminated
608		* @throws IllegalStateException if not terminated and the number
609		* of registered or unarrived parties would become negative
610		*/
611		public int arriveAndDeregister() {
612	<	// similar code to arrive, but too different to merge
524	<	Phaser par = parent;
525	<	int phase;
526	<	for (;;) {
527	<	long s = state;
528	<	phase = phaseOf(s);
529	<	if (phase < 0)
530	<	break;
531	<	int parties = partiesOf(s) - 1;
532	<	int unarrived = unarrivedOf(s) - 1;
533	<	if (parties >= 0) {
534	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
535	<	if (casState
536	<	(s,
537	<	stateFor(phase, parties, unarrived))) {
538	<	if (unarrived == 0) {
539	<	par.arriveAndDeregister();
540	<	reconcileState();
541	<	}
542	<	break;
543	<	}
544	<	continue;
545	<	}
546	<	if (unarrived == 0) {
547	<	if (casState
548	<	(s,
549	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
550	<	((phase + 1) & phaseMask), parties))) {
551	<	releaseWaiters(phase);
552	<	break;
553	<	}
554	<	continue;
555	<	}
556	<	if (par != null && phase != phaseOf(root.state)) {
557	<	reconcileState();
558	<	continue;
559	<	}
560	<	}
561	<	throw new IllegalStateException(badBounds(parties, unarrived));
562	<	}
563	<	return phase;
612	>	return doArrive(true);
613		}
614
615		/**
616	<	* Arrives at the barrier and awaits others. Equivalent in effect
616	>	* Arrives at this phaser and awaits others. Equivalent in effect
617		* to {@code awaitAdvance(arrive())}.  If you need to await with
618		* interruption or timeout, you can arrange this with an analogous
619	<	* construction using one of the other forms of the awaitAdvance
620	<	* method.  If instead you need to deregister upon arrival use
621	<	* {@code arriveAndDeregister}. It is an unenforced usage error
622	<	* for an unregistered party to invoke this method.
619	>	* construction using one of the other forms of the {@code
620	>	* awaitAdvance} method.  If instead you need to deregister upon
621	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
622	>	*
623	>	* <p>It is a usage error for an unregistered party to invoke this
624	>	* method.  However, this error may result in an {@code
625	>	* IllegalStateException} only upon some subsequent operation on
626	>	* this phaser, if ever.
627		*
628	<	* @return the arrival phase number, or a negative number if terminated
628	>	* @return the arrival phase number, or the (negative)
629	>	* {@linkplain #getPhase() current phase} if terminated
630		* @throws IllegalStateException if not terminated and the number
631		* of unarrived parties would become negative
632		*/
633		public int arriveAndAwaitAdvance() {
634	<	return awaitAdvance(arrive());
634	>	// Specialization of doArrive+awaitAdvance eliminating some reads/paths
635	>	final Phaser root = this.root;
636	>	for (;;) {
637	>	long s = (root == this) ? state : reconcileState();
638	>	int phase = (int)(s >>> PHASE_SHIFT);
639	>	int counts = (int)s;
640	>	int unarrived = (counts & UNARRIVED_MASK) - 1;
641	>	if (phase < 0)
642	>	return phase;
643	>	else if (counts == EMPTY || unarrived < 0) {
644	>	if (reconcileState() == s)
645	>	throw new IllegalStateException(badArrive(s));
646	>	}
647	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s,
648	>	s -= ONE_ARRIVAL)) {
649	>	if (unarrived != 0)
650	>	return root.internalAwaitAdvance(phase, null);
651	>	if (root != this)
652	>	return parent.arriveAndAwaitAdvance();
653	>	long n = s & PARTIES_MASK;  // base of next state
654	>	int nextUnarrived = ((int)n) >>> PARTIES_SHIFT;
655	>	if (onAdvance(phase, nextUnarrived))
656	>	n |= TERMINATION_BIT;
657	>	else if (nextUnarrived == 0)
658	>	n |= EMPTY;
659	>	else
660	>	n |= nextUnarrived;
661	>	int nextPhase = (phase + 1) & MAX_PHASE;
662	>	n |= (long)nextPhase << PHASE_SHIFT;
663	>	if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n))
664	>	return (int)(state >>> PHASE_SHIFT); // terminated
665	>	releaseWaiters(phase);
666	>	return nextPhase;
667	>	}
668	>	}
669		}
670
671		/**
672	<	* Awaits the phase of the barrier to advance from the given phase
673	<	* value, returning immediately if the current phase of the
674	<	* barrier is not equal to the given phase value or this barrier
587	<	* is terminated.  It is an unenforced usage error for an
588	<	* unregistered party to invoke this method.
672	>	* Awaits the phase of this phaser to advance from the given phase
673	>	* value, returning immediately if the current phase is not equal
674	>	* to the given phase value or this phaser is terminated.
675		*
676		* @param phase an arrival phase number, or negative value if
677		* terminated; this argument is normally the value returned by a
678	<	* previous call to {@code arrive} or its variants
679	<	* @return the next arrival phase number, or a negative value
680	<	* if terminated or argument is negative
678	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
679	>	* @return the next arrival phase number, or the argument if it is
680	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
681	>	* if terminated
682		*/
683		public int awaitAdvance(int phase) {
684	+	final Phaser root = this.root;
685	+	long s = (root == this) ? state : reconcileState();
686	+	int p = (int)(s >>> PHASE_SHIFT);
687		if (phase < 0)
688		return phase;
689	<	long s = getReconciledState();
690	<	int p = phaseOf(s);
691	<	if (p != phase)
602	<	return p;
603	<	if (unarrivedOf(s) == 0 && parent != null)
604	<	parent.awaitAdvance(phase);
605	<	// Fall here even if parent waited, to reconcile and help release
606	<	return untimedWait(phase);
689	>	if (p == phase)
690	>	return root.internalAwaitAdvance(phase, null);
691	>	return p;
692		}
693
694		/**
695	<	* Awaits the phase of the barrier to advance from the given phase
695	>	* Awaits the phase of this phaser to advance from the given phase
696		* value, throwing {@code InterruptedException} if interrupted
697	<	* while waiting, or returning immediately if the current phase of
698	<	* the barrier is not equal to the given phase value or this
699	<	* barrier is terminated. It is an unenforced usage error for an
615	<	* unregistered party to invoke this method.
697	>	* while waiting, or returning immediately if the current phase is
698	>	* not equal to the given phase value or this phaser is
699	>	* terminated.
700		*
701		* @param phase an arrival phase number, or negative value if
702		* terminated; this argument is normally the value returned by a
703	<	* previous call to {@code arrive} or its variants
704	<	* @return the next arrival phase number, or a negative value
705	<	* if terminated or argument is negative
703	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
704	>	* @return the next arrival phase number, or the argument if it is
705	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
706	>	* if terminated
707		* @throws InterruptedException if thread interrupted while waiting
708		*/
709		public int awaitAdvanceInterruptibly(int phase)
710		throws InterruptedException {
711	+	final Phaser root = this.root;
712	+	long s = (root == this) ? state : reconcileState();
713	+	int p = (int)(s >>> PHASE_SHIFT);
714		if (phase < 0)
715		return phase;
716	<	long s = getReconciledState();
717	<	int p = phaseOf(s);
718	<	if (p != phase)
719	<	return p;
720	<	if (unarrivedOf(s) == 0 && parent != null)
721	<	parent.awaitAdvanceInterruptibly(phase);
722	<	return interruptibleWait(phase);
716	>	if (p == phase) {
717	>	QNode node = new QNode(this, phase, true, false, 0L);
718	>	p = root.internalAwaitAdvance(phase, node);
719	>	if (node.wasInterrupted)
720	>	throw new InterruptedException();
721	>	}
722	>	return p;
723		}
724
725		/**
726	<	* Awaits the phase of the barrier to advance from the given phase
726	>	* Awaits the phase of this phaser to advance from the given phase
727		* value or the given timeout to elapse, throwing {@code
728		* InterruptedException} if interrupted while waiting, or
729	<	* returning immediately if the current phase of the barrier is
730	<	* not equal to the given phase value or this barrier is
643	<	* terminated.  It is an unenforced usage error for an
644	<	* unregistered party to invoke this method.
729	>	* returning immediately if the current phase is not equal to the
730	>	* given phase value or this phaser is terminated.
731		*
732		* @param phase an arrival phase number, or negative value if
733		* terminated; this argument is normally the value returned by a
734	<	* previous call to {@code arrive} or its variants
734	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
735		* @param timeout how long to wait before giving up, in units of
736		*        {@code unit}
737		* @param unit a {@code TimeUnit} determining how to interpret the
738		*        {@code timeout} parameter
739	<	* @return the next arrival phase number, or a negative value
740	<	* if terminated or argument is negative
739	>	* @return the next arrival phase number, or the argument if it is
740	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
741	>	* if terminated
742		* @throws InterruptedException if thread interrupted while waiting
743		* @throws TimeoutException if timed out while waiting
744		*/
745		public int awaitAdvanceInterruptibly(int phase,
746		long timeout, TimeUnit unit)
747		throws InterruptedException, TimeoutException {
748	+	long nanos = unit.toNanos(timeout);
749	+	final Phaser root = this.root;
750	+	long s = (root == this) ? state : reconcileState();
751	+	int p = (int)(s >>> PHASE_SHIFT);
752		if (phase < 0)
753		return phase;
754	<	long s = getReconciledState();
755	<	int p = phaseOf(s);
756	<	if (p != phase)
757	<	return p;
758	<	if (unarrivedOf(s) == 0 && parent != null)
759	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
760	<	return timedWait(phase, unit.toNanos(timeout));
754	>	if (p == phase) {
755	>	QNode node = new QNode(this, phase, true, true, nanos);
756	>	p = root.internalAwaitAdvance(phase, node);
757	>	if (node.wasInterrupted)
758	>	throw new InterruptedException();
759	>	else if (p == phase)
760	>	throw new TimeoutException();
761	>	}
762	>	return p;
763		}
764
765		/**
766	<	* Forces this barrier to enter termination state. Counts of
767	<	* arrived and registered parties are unaffected. If this phaser
768	<	* has a parent, it too is terminated. This method may be useful
769	<	* for coordinating recovery after one or more tasks encounter
766	>	* Forces this phaser to enter termination state.  Counts of
767	>	* registered parties are unaffected.  If this phaser is a member
768	>	* of a tiered set of phasers, then all of the phasers in the set
769	>	* are terminated.  If this phaser is already terminated, this
770	>	* method has no effect.  This method may be useful for
771	>	* coordinating recovery after one or more tasks encounter
772		* unexpected exceptions.
773		*/
774		public void forceTermination() {
775	<	for (;;) {
776	<	long s = getReconciledState();
777	<	int phase = phaseOf(s);
778	<	int parties = partiesOf(s);
779	<	int unarrived = unarrivedOf(s);
780	<	if (phase < 0 ||
781	<	casState(s, stateFor(-1, parties, unarrived))) {
775	>	// Only need to change root state
776	>	final Phaser root = this.root;
777	>	long s;
778	>	while ((s = root.state) >= 0) {
779	>	long next = (s & ~((long)UNARRIVED_MASK)) | TERMINATION_BIT;
780	>	if (UNSAFE.compareAndSwapLong(root, stateOffset, s, next)) {
781	>	// signal all threads
782		releaseWaiters(0);
783		releaseWaiters(1);
689	–	if (parent != null)
690	–	parent.forceTermination();
784		return;
785		}
786		}
#	Line 696 | Line 789 | public class Phaser {
789		/**
790		* Returns the current phase number. The maximum phase number is
791		* {@code Integer.MAX_VALUE}, after which it restarts at
792	<	* zero. Upon termination, the phase number is negative.
792	>	* zero. Upon termination, the phase number is negative,
793	>	* in which case the prevailing phase prior to termination
794	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
795		*
796		* @return the phase number, or a negative value if terminated
797		*/
798		public final int getPhase() {
799	<	return phaseOf(getReconciledState());
799	>	return (int)(root.state >>> PHASE_SHIFT);
800		}
801
802		/**
803	<	* Returns the number of parties registered at this barrier.
803	>	* Returns the number of parties registered at this phaser.
804		*
805		* @return the number of parties
806		*/
#	Line 715 | Line 810 | public class Phaser {
810
811		/**
812		* Returns the number of registered parties that have arrived at
813	<	* the current phase of this barrier.
813	>	* the current phase of this phaser.
814		*
815		* @return the number of arrived parties
816		*/
817		public int getArrivedParties() {
818	<	return arrivedOf(state);
818	>	return arrivedOf(reconcileState());
819		}
820
821		/**
822		* Returns the number of registered parties that have not yet
823	<	* arrived at the current phase of this barrier.
823	>	* arrived at the current phase of this phaser.
824		*
825		* @return the number of unarrived parties
826		*/
827		public int getUnarrivedParties() {
828	<	return unarrivedOf(state);
828	>	return unarrivedOf(reconcileState());
829		}
830
831		/**
#	Line 753 | Line 848 | public class Phaser {
848		}
849
850		/**
851	<	* Returns {@code true} if this barrier has been terminated.
851	>	* Returns {@code true} if this phaser has been terminated.
852		*
853	<	* @return {@code true} if this barrier has been terminated
853	>	* @return {@code true} if this phaser has been terminated
854		*/
855		public boolean isTerminated() {
856	<	return getPhase() < 0;
856	>	return root.state < 0L;
857		}
858
859		/**
860		* Overridable method to perform an action upon impending phase
861		* advance, and to control termination. This method is invoked
862	<	* upon arrival of the party tripping the barrier (when all other
862	>	* upon arrival of the party advancing this phaser (when all other
863		* waiting parties are dormant).  If this method returns {@code
864	<	* true}, then, rather than advance the phase number, this barrier
865	<	* will be set to a final termination state, and subsequent calls
866	<	* to {@link #isTerminated} will return true. Any (unchecked)
867	<	* Exception or Error thrown by an invocation of this method is
868	<	* propagated to the party attempting to trip the barrier, in
869	<	* which case no advance occurs.
864	>	* true}, this phaser will be set to a final termination state
865	>	* upon advance, and subsequent calls to {@link #isTerminated}
866	>	* will return true. Any (unchecked) Exception or Error thrown by
867	>	* an invocation of this method is propagated to the party
868	>	* attempting to advance this phaser, in which case no advance
869	>	* occurs.
870		*
871		* <p>The arguments to this method provide the state of the phaser
872	<	* prevailing for the current transition. (When called from within
873	<	* an implementation of {@code onAdvance} the values returned by
874	<	* methods such as {@code getPhase} may or may not reliably
875	<	* indicate the state to which this transition applies.)
876	<	*
877	<	* <p>The default version returns {@code true} when the number of
878	<	* registered parties is zero. Normally, overrides that arrange
879	<	* termination for other reasons should also preserve this
880	<	* property.
881	<	*
882	<	* <p>You may override this method to perform an action with side
883	<	* effects visible to participating tasks, but doing so requires
884	<	* care: Method {@code onAdvance} may be invoked more than once
885	<	* per transition.  Further, unless all parties register before
886	<	* any arrive, and all {@link #awaitAdvance} at each phase, then
887	<	* you cannot ensure lack of interference from other parties
888	<	* during the invocation of this method.
872	>	* prevailing for the current transition.  The effects of invoking
873	>	* arrival, registration, and waiting methods on this phaser from
874	>	* within {@code onAdvance} are unspecified and should not be
875	>	* relied on.
876	>	*
877	>	* <p>If this phaser is a member of a tiered set of phasers, then
878	>	* {@code onAdvance} is invoked only for its root phaser on each
879	>	* advance.
880	>	*
881	>	* <p>To support the most common use cases, the default
882	>	* implementation of this method returns {@code true} when the
883	>	* number of registered parties has become zero as the result of a
884	>	* party invoking {@code arriveAndDeregister}.  You can disable
885	>	* this behavior, thus enabling continuation upon future
886	>	* registrations, by overriding this method to always return
887	>	* {@code false}:
888	>	*
889	>	* <pre> {@code
890	>	* Phaser phaser = new Phaser() {
891	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
892	>	* }}</pre>
893		*
894	<	* @param phase the phase number on entering the barrier
894	>	* @param phase the current phase number on entry to this method,
895	>	* before this phaser is advanced
896		* @param registeredParties the current number of registered parties
897	<	* @return {@code true} if this barrier should terminate
897	>	* @return {@code true} if this phaser should terminate
898		*/
899		protected boolean onAdvance(int phase, int registeredParties) {
900	<	return registeredParties <= 0;
900	>	return registeredParties == 0;
901		}
902
903		/**
#	Line 807 | Line 907 | public class Phaser {
907		* followed by the number of registered parties, and {@code
908		* "arrived = "} followed by the number of arrived parties.
909		*
910	<	* @return a string identifying this barrier, as well as its state
910	>	* @return a string identifying this phaser, as well as its state
911		*/
912		public String toString() {
913	<	long s = getReconciledState();
913	>	return stateToString(reconcileState());
914	>	}
915	>
916	>	/**
917	>	* Implementation of toString and string-based error messages
918	>	*/
919	>	private String stateToString(long s) {
920		return super.toString() +
921		"[phase = " + phaseOf(s) +
922		" parties = " + partiesOf(s) +
923		" arrived = " + arrivedOf(s) + "]";
924		}
925
926	<	// methods for waiting
926	>	// Waiting mechanics
927
928		/**
929	<	* Wait nodes for Treiber stack representing wait queue
929	>	* Removes and signals threads from queue for phase.
930		*/
931	<	static final class QNode implements ForkJoinPool.ManagedBlocker {
932	<	final Phaser phaser;
933	<	final int phase;
934	<	final long startTime;
935	<	final long nanos;
936	<	final boolean timed;
937	<	final boolean interruptible;
938	<	volatile boolean wasInterrupted = false;
939	<	volatile Thread thread; // nulled to cancel wait
834	<	QNode next;
835	<	QNode(Phaser phaser, int phase, boolean interruptible,
836	<	boolean timed, long startTime, long nanos) {
837	<	this.phaser = phaser;
838	<	this.phase = phase;
839	<	this.timed = timed;
840	<	this.interruptible = interruptible;
841	<	this.startTime = startTime;
842	<	this.nanos = nanos;
843	<	thread = Thread.currentThread();
844	<	}
845	<	public boolean isReleasable() {
846	<	return (thread == null ||
847	<	phaser.getPhase() != phase ||
848	<	(interruptible && wasInterrupted) ||
849	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
850	<	}
851	<	public boolean block() {
852	<	if (Thread.interrupted()) {
853	<	wasInterrupted = true;
854	<	if (interruptible)
855	<	return true;
856	<	}
857	<	if (!timed)
858	<	LockSupport.park(this);
859	<	else {
860	<	long waitTime = nanos - (System.nanoTime() - startTime);
861	<	if (waitTime <= 0)
862	<	return true;
863	<	LockSupport.parkNanos(this, waitTime);
864	<	}
865	<	return isReleasable();
866	<	}
867	<	void signal() {
868	<	Thread t = thread;
869	<	if (t != null) {
870	<	thread = null;
931	>	private void releaseWaiters(int phase) {
932	>	QNode q;   // first element of queue
933	>	Thread t;  // its thread
934	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
935	>	while ((q = head.get()) != null &&
936	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
937	>	if (head.compareAndSet(q, q.next) &&
938	>	(t = q.thread) != null) {
939	>	q.thread = null;
940		LockSupport.unpark(t);
941		}
942		}
874	–	boolean doWait() {
875	–	if (thread != null) {
876	–	try {
877	–	ForkJoinPool.managedBlock(this, false);
878	–	} catch (InterruptedException ie) {
879	–	}
880	–	}
881	–	return wasInterrupted;
882	–	}
883	–
943		}
944
945		/**
946	<	* Removes and signals waiting threads from wait queue.
946	>	* Variant of releaseWaiters that additionally tries to remove any
947	>	* nodes no longer waiting for advance due to timeout or
948	>	* interrupt. Currently, nodes are removed only if they are at
949	>	* head of queue, which suffices to reduce memory footprint in
950	>	* most usages.
951	>	*
952	>	* @return current phase on exit
953		*/
954	<	private void releaseWaiters(int phase) {
955	<	AtomicReference<QNode> head = queueFor(phase);
956	<	QNode q;
957	<	while ((q = head.get()) != null) {
958	<	if (head.compareAndSet(q, q.next))
959	<	q.signal();
954	>	private int abortWait(int phase) {
955	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
956	>	for (;;) {
957	>	Thread t;
958	>	QNode q = head.get();
959	>	int p = (int)(root.state >>> PHASE_SHIFT);
960	>	if (q == null || ((t = q.thread) != null && q.phase == p))
961	>	return p;
962	>	if (head.compareAndSet(q, q.next) && t != null) {
963	>	q.thread = null;
964	>	LockSupport.unpark(t);
965	>	}
966		}
967		}
968
969	+	/** The number of CPUs, for spin control */
970	+	private static final int NCPU = Runtime.getRuntime().availableProcessors();
971	+
972		/**
973	<	* Tries to enqueue given node in the appropriate wait queue.
974	<	*
975	<	* @return true if successful
973	>	* The number of times to spin before blocking while waiting for
974	>	* advance, per arrival while waiting. On multiprocessors, fully
975	>	* blocking and waking up a large number of threads all at once is
976	>	* usually a very slow process, so we use rechargeable spins to
977	>	* avoid it when threads regularly arrive: When a thread in
978	>	* internalAwaitAdvance notices another arrival before blocking,
979	>	* and there appear to be enough CPUs available, it spins
980	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
981	>	* off good-citizenship vs big unnecessary slowdowns.
982		*/
983	<	private boolean tryEnqueue(QNode node) {
904	<	AtomicReference<QNode> head = queueFor(node.phase);
905	<	return head.compareAndSet(node.next = head.get(), node);
906	<	}
983	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
984
985		/**
986	<	* Enqueues node and waits unless aborted or signalled.
986	>	* Possibly blocks and waits for phase to advance unless aborted.
987	>	* Call only from root node.
988		*
989	+	* @param phase current phase
990	+	* @param node if non-null, the wait node to track interrupt and timeout;
991	+	* if null, denotes noninterruptible wait
992		* @return current phase
993		*/
994	<	private int untimedWait(int phase) {
995	<	QNode node = null;
996	<	boolean queued = false;
997	<	boolean interrupted = false;
994	>	private int internalAwaitAdvance(int phase, QNode node) {
995	>	releaseWaiters(phase-1);          // ensure old queue clean
996	>	boolean queued = false;           // true when node is enqueued
997	>	int lastUnarrived = 0;            // to increase spins upon change
998	>	int spins = SPINS_PER_ARRIVAL;
999	>	long s;
1000		int p;
1001	<	while ((p = getPhase()) == phase) {
1002	<	if (Thread.interrupted())
1003	<	interrupted = true;
1004	<	else if (node == null)
1005	<	node = new QNode(this, phase, false, false, 0, 0);
1006	<	else if (!queued)
1007	<	queued = tryEnqueue(node);
1008	<	else
1009	<	interrupted = node.doWait();
1001	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
1002	>	if (node == null) {           // spinning in noninterruptible mode
1003	>	int unarrived = (int)s & UNARRIVED_MASK;
1004	>	if (unarrived != lastUnarrived &&
1005	>	(lastUnarrived = unarrived) < NCPU)
1006	>	spins += SPINS_PER_ARRIVAL;
1007	>	boolean interrupted = Thread.interrupted();
1008	>	if (interrupted || --spins < 0) { // need node to record intr
1009	>	node = new QNode(this, phase, false, false, 0L);
1010	>	node.wasInterrupted = interrupted;
1011	>	}
1012	>	}
1013	>	else if (node.isReleasable()) // done or aborted
1014	>	break;
1015	>	else if (!queued) {           // push onto queue
1016	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
1017	>	QNode q = node.next = head.get();
1018	>	if ((q == null || q.phase == phase) &&
1019	>	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
1020	>	queued = head.compareAndSet(q, node);
1021	>	}
1022	>	else {
1023	>	try {
1024	>	ForkJoinPool.managedBlock(node);
1025	>	} catch (InterruptedException ie) {
1026	>	node.wasInterrupted = true;
1027	>	}
1028	>	}
1029	>	}
1030	>
1031	>	if (node != null) {
1032	>	if (node.thread != null)
1033	>	node.thread = null;       // avoid need for unpark()
1034	>	if (node.wasInterrupted && !node.interruptible)
1035	>	Thread.currentThread().interrupt();
1036	>	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
1037	>	return abortWait(phase); // possibly clean up on abort
1038		}
928	–	if (node != null)
929	–	node.thread = null;
1039		releaseWaiters(phase);
931	–	if (interrupted)
932	–	Thread.currentThread().interrupt();
1040		return p;
1041		}
1042
1043		/**
1044	<	* Interruptible version
938	<	* @return current phase
1044	>	* Wait nodes for Treiber stack representing wait queue
1045		*/
1046	<	private int interruptibleWait(int phase) throws InterruptedException {
1047	<	QNode node = null;
1048	<	boolean queued = false;
1049	<	boolean interrupted = false;
1050	<	int p;
1051	<	while ((p = getPhase()) == phase && !interrupted) {
1052	<	if (Thread.interrupted())
1053	<	interrupted = true;
1054	<	else if (node == null)
1055	<	node = new QNode(this, phase, true, false, 0, 0);
950	<	else if (!queued)
951	<	queued = tryEnqueue(node);
952	<	else
953	<	interrupted = node.doWait();
954	<	}
955	<	if (node != null)
956	<	node.thread = null;
957	<	if (p != phase || (p = getPhase()) != phase)
958	<	releaseWaiters(phase);
959	<	if (interrupted)
960	<	throw new InterruptedException();
961	<	return p;
962	<	}
1046	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
1047	>	final Phaser phaser;
1048	>	final int phase;
1049	>	final boolean interruptible;
1050	>	final boolean timed;
1051	>	boolean wasInterrupted;
1052	>	long nanos;
1053	>	long lastTime;
1054	>	volatile Thread thread; // nulled to cancel wait
1055	>	QNode next;
1056
1057	<	/**
1058	<	* Timeout version.
1059	<	* @return current phase
1060	<	*/
1061	<	private int timedWait(int phase, long nanos)
1062	<	throws InterruptedException, TimeoutException {
1063	<	long startTime = System.nanoTime();
1064	<	QNode node = null;
1065	<	boolean queued = false;
1066	<	boolean interrupted = false;
1067	<	int p;
1068	<	while ((p = getPhase()) == phase && !interrupted) {
1057	>	QNode(Phaser phaser, int phase, boolean interruptible,
1058	>	boolean timed, long nanos) {
1059	>	this.phaser = phaser;
1060	>	this.phase = phase;
1061	>	this.interruptible = interruptible;
1062	>	this.nanos = nanos;
1063	>	this.timed = timed;
1064	>	this.lastTime = timed ? System.nanoTime() : 0L;
1065	>	thread = Thread.currentThread();
1066	>	}
1067	>
1068	>	public boolean isReleasable() {
1069	>	if (thread == null)
1070	>	return true;
1071	>	if (phaser.getPhase() != phase) {
1072	>	thread = null;
1073	>	return true;
1074	>	}
1075		if (Thread.interrupted())
1076	<	interrupted = true;
1077	<	else if (nanos - (System.nanoTime() - startTime) <= 0)
1078	<	break;
1079	<	else if (node == null)
1080	<	node = new QNode(this, phase, true, true, startTime, nanos);
1081	<	else if (!queued)
1082	<	queued = tryEnqueue(node);
1083	<	else
1084	<	interrupted = node.doWait();
1085	<	}
1086	<	if (node != null)
1087	<	node.thread = null;
1088	<	if (p != phase || (p = getPhase()) != phase)
1089	<	releaseWaiters(phase);
1090	<	if (interrupted)
1091	<	throw new InterruptedException();
1092	<	if (p == phase)
1093	<	throw new TimeoutException();
1094	<	return p;
1076	>	wasInterrupted = true;
1077	>	if (wasInterrupted && interruptible) {
1078	>	thread = null;
1079	>	return true;
1080	>	}
1081	>	if (timed) {
1082	>	if (nanos > 0L) {
1083	>	long now = System.nanoTime();
1084	>	nanos -= now - lastTime;
1085	>	lastTime = now;
1086	>	}
1087	>	if (nanos <= 0L) {
1088	>	thread = null;
1089	>	return true;
1090	>	}
1091	>	}
1092	>	return false;
1093	>	}
1094	>
1095	>	public boolean block() {
1096	>	if (isReleasable())
1097	>	return true;
1098	>	else if (!timed)
1099	>	LockSupport.park(this);
1100	>	else if (nanos > 0)
1101	>	LockSupport.parkNanos(this, nanos);
1102	>	return isReleasable();
1103	>	}
1104		}
1105
1106		// Unsafe mechanics
#	Line 1001 | Line 1109 | public class Phaser {
1109		private static final long stateOffset =
1110		objectFieldOffset("state", Phaser.class);
1111
1004	–	private final boolean casState(long cmp, long val) {
1005	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
1006	–	}
1007	–
1112		private static long objectFieldOffset(String field, Class<?> klazz) {
1113		try {
1114		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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